This invention relates to a process for the fabrication of a semiconductor die.
Miniaturization and slimming of electrical and electronic equipment has led to a need for thinner semiconductor dies. One way to produce a thinner semiconductor die is to remove excess material from the back side of the semiconductor wafer, from which the individual dies are diced. In addition to the usual semiconductor circuitry on the wafers, some of the wafers have been micro-fabricated with via holes using through-silicon-via processes (TSV). The removal of the excess wafer typically occurs in a grinding process, commonly called back side grinding. When the wafer is diced into individual semiconductor circuits before the wafer is thinned, the process is called “dicing before grinding” or DBG.
In a DBG process, a support tape, called a dicing tape, is applied to the back side of the wafer and dicing grooves are cut, by saw or laser, between the circuits to a depth that will meet or pass the level to which the back side grinding will be done. The via holes are fabricated at this time using TSV processes. The dicing tape is removed from the back side of the wafer and another support tape is applied to the top side of the wafer to protect the circuitry during back side grinding. The material on the back side of the wafer is removed until the via holes and dicing grooves are reached, which singulates the dies.
After the backgrinding step, a film adhesive coating (usually pre-formed to the shape of the wafer) is laminated to the entire back side of the wafer. This adhesive is used later to attach the individual dies to their selected substrates. The use of the film adhesive requires an additional sawing step to cut the film. Without the additional sawing step, the dies will remain connected to each other by the adhesive film, and cannot be picked up and placed on their designated substrates.
The grinding process tends to shift the dies around, so it is difficult to use a mechanical saw as the dicing streets are no longer straight lines. Instead, a laser saw, which can be programmed to cut through the uneven dicing grooves, is used. If adhesive pastes, some of which can be UV curable, are used instead of film, the adhesive coating will cover the dicing streets, again requiring the use of a laser saw. Using the laser saw is a slow process, and the laser saw itself is an expensive and additional piece of equipment.
In another DBG process, the adhesive can be accurately applied onto the back side of diced wafers using ink jet head. However, this method is extremely slow and requires extremely low viscosity liquids.
Processes for pre-applied underfill have similar problems.
The current invention provides a solution to these problems.